X-ray tube



Sept- 17, 1946- A. vERHoEl-F I X- RAY TUB E Filed Jan. 11,; 194s i 16, Iil' y@ x zizi/l sa :5154 2:46 a; iffA me/whoa,

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Aranu Patented Sept. 17, 1946 2,407,857 X-RAY TUBE Adrianus Verhoeff,Eindhoven, Netherlands, assignor to Hartford National Bank & TrustCompany, Hartford, Conn., trustee Application January 11, 1943, SerialNo. 472,068 In the Netherlands February 27, 1941 (Cl. Z50-143) 10Claims. 1

X-ray tubes having a comparatively great mean load require measures forcooling the anode. Various means may be used to withdraw heat from theanode. In tubes for diagnostic work the operating temperature of theanode must remain far below the maximum admissible anode temperature toprevent heat shock. The usual expedient is to fix a heat conductor tothe anode, for example conductor shaped in the form of a metal rod whichextends through the wall of the tube behind the anode and has aradiating surface outside the tube.

With tubes comprising a safety jacket the presence of such a heatradiating member having the potential of the anode is inconvenient forseveral reasons and it has therefore previously been suggested that theheat transfer should be effected by radiation from the anode towardsthat part of the tube wall which surrounds the anode instead of beingeffected by transmission. By this wall which is generally maintained atearth potential,

the heat can be readily transmitted to the surrounding air or to acooling medium.

Although this means of cooling the anode yielded satisfactory resultsthanks to a combinaference of not more than 300 C. away from the vanodeto the space outside the vacuum of the tube. The term wholly or in partis to be understood to mean here that in a radial direction, and hencenot in an axial direction, the body may consist wholly of insulatingmaterial or may consist of alternating laminae of conducting andinsulating materials.

It is essential that the insulating material be capable of withstandingthe full tension existing between the anode and earth, said tensionbeing about half the operating voltage of the tube.`

It is dimcult to manufacture and place in position an insulator thatfits so accurately around the anode that a satisfactory heat conducting,

contact may be set up between the wall of the p anode and that of theinsulator. According to .the invention, this difficulty can be obviatedby a resilient member of goodheat conductivity which engages the wallsof the intermediate space with slight pressure and transmits the heatfrom one wall to the other. This affords good heat conduction andenables free expansion and con, traction due to temperature changes.This resilient member may be constituted for example by a cylinder ofcorrugated sheet metal.

The principle of the invention may be carried -into practice in variousways, The insulator may y form part of the outer Wall of the tube :andthus serve to absorb both the electric voltage and the air pressure.

As an alternative, the insulator may be wholly arranged within thevacuum of the tube., In this case, the heat has therefore still to `beconducted from the insulator to that part of the outer wall of the tubeby which it is surrounded and which in this case may be of metal. Inorder to assist good heat transmission between the insulator and thetube wall, it is preferable that a resilient member, for example a metalsleeve of corrugated sheet metal should be arranged in the mannermentioned before for the conveyance of the heat from the anode to theinsulator.

The insulator may be made of ceramic material, for example china. Thismaterial is capable of withstanding heat, may be readily freed fromgases and is Vgenerally a suilicient heat conductor and electricalinsulator.

In the construction according to the invention the heat is conductedaway by a body which is required to be a good electrical insulator.Although as a rule the heat conductivity of electrical insulators ismuch less than that of metals, sufficient heat can be conducted away inthis case by the insulator due to the fact that the direction in whichthe energy ows off is normal to the surface and this latter may be madecomparatively large so that but little heat per unit of section needs tobe conducted away. Moreover, the heat has only to traverse acomparatively short path. The conditionsare consequently just thereverse as compared with tubes having a cooler at the end, because inthe latter case the section of the (metal) heat. conductor is muchsmaller and its length is much greater as compared with the tubeaccording to the invention.

In order to increase the surface over which theV heat dissipation isdistributed the anode as a whole need not be made particularly long butit is suflicient to shape it into the form of a hollow tube, for examplea cylindrical tube, which dissipates the heat and transmits it to thesurrounding body and which comprises a bottom or intermediate wallcarrying the anode mirror.

The circumstance that the anode is in heatconducting contact with abody7 surrounding it may be taken advantage of to cause it to be sosupported by this body that that part of the wall which seals the tubeat the end behind the anode is not given any mechanical load by theanode weight. This latter part which thus only serves for insulation andfor sealing the vacuum'must give passage to the current supply lead ofthe anode which may therefore be very thin so that heat is not conductedaway along this path. The tube end which can be closed by a cable endpiece thus remains cool due to the fact that a direct heat-conductingconnection to the anode is missmg.

.For sealing the tube at the ends use may also be made of disc-shapedglass-like members comprising finely divided cavities (so-called spongeglass) which permits metals and insulating materials having widelydiierent coeicients of expansion to be sealed together to thereby obtaina vacuum-tight seal.

In order that the invention maybe clearly understood and readily carriedinto eiect it will now be set out more fully with reference to theaccompanying drawing in which two forms of construction of X-ray tubesaccording to the invention are shown in section. By means thereof somedetails obtained by further development of' the invention will bementioned.

' Fig. l is a longitudinal sectional view of an X- ray tube having aheat-conducting insulating body arranged entirely within the tube.

Fig, 2 is a cross-sectional View of the same tube taken on the planeI-I.

Fig. 3 shows a tube in which the heat conducting insulating bodyconstitutes the outer wall of the tube.

Referring to the drawing, 1 designates an exhausted cylindrical metalvessel closed at the ends by glass sealing pieces 2 and 3. A cylindricalbody of electrically insulating material, for example china or otherceramic material is gripped in the metal vessel b-y means of a resilientsleeve 4 of corrugated sheet metal of good heat conductivity',A forexample copper.

The anode of the X-ray tube is gripped within the body 5 by a likewiseresilient sleeve B of corrugated plate-shaped material. The anodecomprises a cylindrical part 'lv and a block 8 both of metal kof goodheat conductivity, for example copper. The cylinder 1 may be shrunkround the block 3 so as to afford good heat conduction.

The anode has secured to it a supply conductor 9 which is passed throughthe sealing piece 2 by means of a small metal disc li) sealed to theglass. The cathode Il is secured to the sealing piece 3 and has a normalconstruction,` details such as the leading-in wires sealed in the pinchand the filament being therefore omitted in the drawing. When the tubeis in use the electrons are propelled by the electric neld between thetwo electrodes at such a speed against the anode mirror I2 that X raysare generated in situ. Essentially,

l however, the energy of the electrons is converted into heat andsecondary electrons are also dislodged.

The X rays are absorbed for the greater part by the wall of the tube andother parts (all of which are not shown) which jointly surround theanode and in part may be provided deliberately for this purpose. Anarrow beam of rays is transmitted. For this purpose the cylindricalpart 1 of the anode 8 has an aperture i3 formed of the cathode.

in it, the body 5 is locally thinned at I4, the sleeves 4 and 5 have acorresponding aperture formed in them and the metal wall I comprises awindow closed by a thin small glass plate l5.

The heat is rapidly dispersed about the block t and thence it istransmitted to the cylinder l. The latter gives theanode a large surfaceof contact with the resilient sleeve 6 which in turn is in contact overa large surface with the china part 5.

Although the heat transmitted through each unit section of the part 5 isless than if it were made of metal the large extensiveness of thesection which contributes towards the conveyance of heat and the shortdistance through which the heat has to be conveyed enable the heat toescape rapidly.

It is true that the spaces between the anode and the china part 5 andthose between the latter and the tube wallare only filled in part 'butthe gripping sleeves and 5. may be made of a metal having a much higherspecific conductivity than the insulator 5.

The outside of the wallfi may, if necessary, be cooled artiliciallyv bya circulating gaseous or liquid cooling medium or by the provision ofcooling ribs.

The withdrawal of heat from the wall l to the glass sealing pieces isavoided by the presence of Y thinned` edges l5. In addition, radiationof heat from the anode to the sealing piece 2- is prevented bythe bottomIl of the insulator 5'. The current lead 9 is so thin and klong that noappreciable heat'transmission occurs alongr it. The glass sealing piece2 and the cable end-piece to be arranged thereon are thus safe-guardedVagainst heating.

' With X-ray'tubes of they construction hitherto in use the anode issupported by the re-entrant glass edge ofthe tube wall.

The invention permitsa sturdier construction to be obtained. It enablesthe anode to be carried solely by therside wall of the tube by unitingthe resilient sleeves 4 and' and the insulator 5 with the anode and themetal wall l to form an Aunshakable unit, forY example by gripping, as

shown. The glass part 2 of the wall which seals the tube at the end'behind the anode is thus not given any mechanical load by the weight ofthe anode and thus the risk of breakage which is always impending inother tubes is averted.

The metal cylindricalV body l is also used for a further purpose. It islengthened towards the side This arrangement has the Vadvantage that thepart extending to the other side can be shorter and the heat is morereadily' distributed about the entire length of the cylinder because itcan flow from the centre to both sides moreover, the tube acts as ascreen against secondary electrons. In order that this function may bemost effective the cylindrical body is provided with a bottom i8 whichhas, of course, formed in it an aperture for the passage of the beam ofcathode-rays. In addition, this aperture has an upright edge i9 turnedtowards the anode mirror in order also to retain electrons moving in adirection at a large angle with the axis of the tube, such as tertiaryelectrons proceeding from the inner wall of the cylinder l.

In so far as charged particles may still emerge `from the dischargespace they are retained by the is formed by a block 2| and a cylinder22, the block 2| carrying the anode mirror 23.

Again, the cylinder 22' is mounted an insulator 25 by means of aresilient sleeve 24 of corrugated sheet metal.

The insulator 25 constitutes the envelope of the tube, and glass sealingpieces 26 and 21 are sealed to theedges of the insulator at 28 and 29.The insulator may be of china or of similar ceramic material to whichglass can be fused. The anode is supported by the insulator 25 only andthe sealing piece 2E solely serves for vacuum sealing the envelope andfor the leading-through of the supply conductor 3D to the anode. For thepurpose of increased safety the insulator may be coated on the outsidewith a layer of conductive mate rial (not shown). a

Similarly, the sealing piece 21 serves solely for sealing the vacuum andfor leading-through of the supply leads 3l and 32 to the cathode. Thelatter are secured to studs which are arranged in a metal plate 35 fromwhich they are insulated by glass beads 33 and 34 t0 the edge of whichthe glass Sealing piece 21 is sealed.

The cathode shell 36 is supported within the insulator 25 in a mannersimilar to the anode by means of a disc 31 having a bent-over edge 38which is rendered resilient by the provision of a plurality of slits 39.

The heat produced in the anode in the use of the tube passes to thecylinder 22 and hence is led by the resilient sleeve 24 through a largesectional surface of the insulator 25 towards the outer surface of thetube, where it is dissipated by radiation or carried away by othermeans.

What I claim is:

1. An X-ray tube comprising an evacuated tubular envelope, an anodemember having a heat-generating portion and being arranged within saidenvelope with its peripheral surface adjacent to and spaced from theinner surface of the envelope, and means to directly connect the saidadjacent surfaces in heat conducting relationship comprising a memberofgood heat con-Y ductivity whereby to transfer the heat generated at saidportion to said envelope in a radial direction from the anode member andsubstantially entirely by conduction.

2. An X-ray tube comprising an evacuated tubular envelope, an anodemember having a heatgenerating portion and being arranged within saidenvelope with its peripheral surface adjacent to the inner surface ofthe envelope, and means to directly connect the said adjacent sur-4faces in heat conducting relationship comprising a resilient member ofgood heat conductivity, the heat generated at said portion beingtransferred to said envelope in a radial direction from the anode memberand substantially entirely by con- V duction through said resilientmember.

3. An X-ray tube comprising an evacuated tuto the inner surface of theenvelope, and means to directly connect the said adjacent surfaces inheat conducting relationship co-mprising an electrical insulating memberand a resilient member.;V

of good heat-conductivity surrounding said anode member and interposedbetween the said adjacent surfaces, the heat generated at said portionbeing transferred tosaid envelope in a radial direction from the anodemember and substantially entirely by conduction through said insulatingand'resilient members.

5. An X-ray tube comprising an evacuated tubular envelope, a hollowcylindrical anode member having a wall portion provided with an anodemirror and being arranged with its peripheral surface adjacent to theinner surface of the envelope, and means to directly connect the saidadjacent surfaces in heat conducting relationship comprising anelectrically insulating ceramic sleeve member and a cylindricalcorrugated sheet-metal member 'surrounding the cylindrcal anode memberand interposed between the said adjacent surfaces, the heat generated atthe anode mirror being transferred to `said envelope a in a radialdirection from said anode member and substantially entirely byconduction through said insulating and sheet-metal member.

6. An X-ray tube comprising an evacuated envelope, and a cathode member,an anode member spaced apart and enclosed within said envelope, saidanode member comprising an anode mirror, a hollow cylindrical elementenclosing the anode mirror, and means to collect secondary electronsfrom the anode mirror comprising a portion of the cylindrical elementextending beyond the said mirror towards the cathode member, saidcylindrical element being arranged within the envelope with itsperipheral surface adjacent to the inner surface of the envelope, and

means to directly connect the said adjacent surfaces in heat conductingrelationship comprising a member of goed heat conductivity whereby totransfer the heat generatedV at the anode mirror to said envelope in aradial direction `from said cylindrical element and substantiallyentirely by conduction.

1. A'n X-ray tube comprisingy an evacuated cylindrical metal envelope,an anode member within said envelope comprising a cylindrical metalsleeve arranged within the envelope with its peripheral surface adjacentto the inner surface of the envelope, an anode mirror within said sleeveand secured to the inner wall thereof, said anode sleeve having aportion which extends beyond the anode mirrorand is provided with anaperture in the wall thereof adjacent to the anode mirror and whichcomprises a flange portion having its edge inwardly facing the anodemirror, and means to directly connect the said adjacent surfaces in heatconducting relationship, said means comprising a cylindrical electricalinsulating ceramic member surrounding the anode member 'and extendingbeyond the said flange portion thereof, a cylindrical corrugated sheetmetal member interposed between and contacting the adjacently positionedsurfaces of the ceramic and anode members and a cylindrical corrugatedsheet metal member interposed between and contacting the adjacentlylpositioned surfaces of the ceramic member and the envelope, the heatgenerated at the said anode mirror `being transferred to the envelopeina.

radial direction from the anode member and substantially entirely byconduction through said cylindrical corrugated members and said ceramicmember.

8. An X-ray tube comprising an evacuated tubular envelope, an anodemember having aheat `generating portion and being yarranged within yyaidenvelope with its peripheral surface adjacent to and spaced from theinner surface of the envelope, said anode member being supported withinsaid envelope substantially entirely by the surrounding portion of theenvelope, and means to directly connect the said adjacent surfaces inheat conducting relationship comprising a member of good heatconductivity whereby to vtransfer the heat generated at the said portionof the anode member to the envelope in a radialdirection from the anodemember and substantially entirely by conduction.

9. An X-ray tube comprising an evacuated tubular envelope, a sealingmember closing one end of the envelope, an anode member having a heatgenerating portion and being arranged within the envelope with itsperipheral surface adjacent to the inner surface of the envelope, avoltage supply conductora for the anode member heat conduction from theanode member to said sealing member. Y

10. An X-ray tube comprising an evacuated tubular envelope', an anodemember having a heat-generating portion and being arranged within saidenvelope with its peripheral surface adjacent to and spaced from andelectrically insulated from .the inner surface of the envelope, andmeans to directly connect the said adjacent surfaces in heat conductingrelationship co-m- Y prisingv a member of good heat conductivity wherebyto transfer the heat generated at said portion to said envelope in. aradial direction from the anode member and substantially entirely byccnduction.

Y v ADRIANUS VERHOEFF.

